Back in December, I noted that Michigan's implementation of the ACA's Medicaid expansion provision had achieved an impressive 99.4% of it's theoretical maximum enrollment. Official state administration estimates pegged the number of Michiganders eligible for the program at around 477,000, and as of 12/08/14, enrollment had hit 474K.

Other estimates had Michigan's eligible population as being higher--perhaps 500,000, so I didn't think too much of it at the time. Besides, population shifts, changes in the economy and so forth could mean that an estimate from last spring had shifted up or down a bit.

Even so, as the official enrollment total broke 500K, then 510K, then 530K, I noted each increase, with increasing curiosity about the discrepancy.